The development of C. elegans hermaphrodites is generally highly reproducible under laboratory conditions. For example, the pattern of somatic programmed cell death (PCD) and establishment of left-right (L/R) handedness in the arrangement of internal organs in hermaphrodites are virtually invariant across large numbers of animals. In contrast, we have found that both N2 and many wild isolates of C. elegans males show frequent “errors,” indicating that that the fidelity of male development is often relaxed and varies widely between wild isolates. We have observed that particular sensory rays in the male tail are often missing as an apparent result of inappropriate PCD, indicating that repression of EGL-1-dependent PCD is defective in many natural isolates. Further, the L/R arrangement of the gut and gonad, while essentially invariant in hermaphrodites and in males of some wild isolates, shows frequent reversals in males of other isotypes, with a reversal rate as high as ~30% at 25oC. Defects in the normal trajectory of gonad migration were also seen in some, but not all of the isotypes; however, these migration errors do not correlate with the L/R organ handedness phenotype across different isotypes. These errors in PCD and L/R handedness are not characteristic of all representatives of the species, as some isolates, unlike N2, nearly always make “perfect” tails and show fully stereotyped organ handedness. Moreover, such defects in male development are not explained by the androdioecious nature of C. elegans, in which males are of low significance to propagation of the species, as we have observed both kinds of defects in gonochoristic (male/female) species. Analysis of RILs made from isotypes that are high-fidelity and low-fidelity for both the stochastic PCD and L/R reversal phenotypes indicate that both traits are multigenic. Finally, we found that a strain that is high fidelity for both developmental processes also shows low variation in two hermaphrodite characteristics: variance in germline stem cell number and in length of newly hatched L1s. In contrast, a strain that is low-fidelity for the two male traits shows high variation in these hermaphrodite parameters. These findings raise the possibility that global differences in the fidelity of development may vary between different isolates of the species. .
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